In many applications, it is desirable to provide an amplifier having a linear function, especially in level control systems and the like. Further, in many specialized applications it is essential that the system have a fast response time and, consequently, the amplifier circuitry, as well as any control circuitry associated therewith, must have a fast response time. The conventional solution to the linearization of a function of the type displayed by amplifier circuitry incorporating a plurality of cascaded multipliers, is to use an exponential gain device in a feedforward control circuit. However, such circuitry is extremely complex, relatively slow and tends to be unstable and difficult to compensate for temperature variations.